The present invention relates to tool tip and tool body assemblies.
It is known to provide a separate and replaceable tool tip for attachment to a tool body. For example, it is known to provide a drill bit in the form of a drill bit tip that is attachable to a drill bit body. It is also possible to provide such an arrangement in a milling or boring tool, such as in a ball nose end mill. The drill bit tip may be made of a harder material than the drill bit body because the drill bit tip tends to be exposed to the greatest forces. The drill bit body may be made of a less hard, and typically less expensive material. Because the drill bit tip can comprise a relatively small percentage of the total amount of material making up the drill bit, the overall expense of the drill bit can be minimized. Moreover, the expected life of the drill bit having a harder drill bit tip can be enhanced relative to drill bits made entirely of softer material. The cost of replacing a harder drill bit tip will typically be lower than the cost of replacing an entire drill bit made of the same material as the drill bit tip. U.S. Pat. Nos. 4,950,108 and 4,684,298 disclose drill assemblies including a drill body and a replaceable drill bit tip and are incorporated by reference herein.
Typically, the drill bit tip and the drill bit body are secured together by one or more, usually two, fasteners, such as bolts or screws extending through holes in the drill bit tip into threaded holes in the drill bit body. Because torsional forces transmitted between the drill bit tip and the drill body tend to be high, it is necessary to use relatively large fasteners on the assembly. The use of large fasteners results in a loss of surface area at the tip of the drill bit tip, and can interfere with the operation of the drill. Moreover, the use of large fasteners makes it difficult to enjoy the advantages of a separate hard drill bit tip and softer drill bit body in drill bits of small sizes or even in drill bits of larger sizes that are intended for use in drilling hard materials. Further still, it is often necessary to provide bushings in the drill bit tip to avoid excessive play between the drill bit tip and the drill bit body during operation. It is desirable to provide a tool tip and tool body assembly that permits the use of small fasteners to secure together the tool tip and the tool body, yet still permits transmission of torque between the tool tip and the tool body to the same or a greater degree than assemblies wherein larger fasteners are used, and avoids problems of excessive play between the tool tip and the tool body.
Swedish Patent Application No. 9501687-9 discloses a drill body and separate drill bit tip assembly wherein the drill bit tip is secured to the drill body by a central bolt extending through the drill body. The drill bit tip is provided with an internal thread for mating with the bolt. Facing surfaces of the drill bit tip and the drill body are provided with mating parallel grooves and ridges. It is desirable to provide a tool tip and tool body assembly that does not require a central bore through the tool body.
In accordance with an aspect of the present invention, a tool tip and tool body assembly is provided. The tool tip has a first end for contacting a workpiece and a second end, the second end having a patterned surface of recesses and protrusions, and at least one through hole extending through the tool tip from the second end. The tool body has a first end having a patterned surface corresponding to the patterned surface of the tool tip for mating with the patterned surface of the tool tip, and at least one threaded hole adapted to align with the at least one through hole in the tool tip. At least one fastener having a threaded end and a securing end is provided, the fastener extending through the at least one through hole such that the securing end abuts against a surface in the at least one through hole, the threaded end mating with threads in the threaded hole. Torque is transmitted between the tool tip and the tool body solely by the at least one fastener and the patterned surface of the tool tip and the patterned surface of the tool body.